Multi-speed precision gear box



Aug. 28, 1962 E. K. ROWLEY ETAL MULTI-SPEED PRECISION GEAR BOX Filed July 21, 1960 3 Sheets-Sheet l FigZ FigA

ATTORNEY INV ENTORS Aug. 28, 1962 E. K. ROWLEY ET AL 3,051,018

MULTI-SPEED PRECISION GEAR Box Filed July 21, 1960 5 sheets-sheet 2 Fig. s2

2 INYEORS S @Mem Figi@BY MM Mam ATTORNEY Aug. 28, 1962 E. K. ROWLEY ET AL 3,051,018

MULTI-SPEED PRECISION GEAR Box Filed July 21, 1960 5 sheets-sheet s f me@ rates 3,051,013 MULTI-SPEED PRECISHN GEAR BOX Edward Kenneth Rowley, Beloeil Station, Quebec, and

Donald Corey West, Beloeil, Quebec, Canada, assignors to Canadian Industries Limited, Montreal, Quebec,

Canada, a corporation of Canada Filed July 21, 1960, Ser. No. 44,366 11 Claims. (Cl. 74-681) The present invention relates to multi-speed transmission systems, and particularly to such systems as are adapted to provide a finite number of different speeds.

Various types of multi-speed transmission systems have heretofore been devised, and in instances where a comparatively large number of different speeds are to be obtained, it has been suggested that an infinitely variable speed drive be used. However, infinitely variable speed drives generally are so constructed that it is difiicult to obtain a reproduction of a previous operation by means of a setting scale. More particularly, in the infinitely variable speed devices, ya scale is normally provided and the output obtained supposedly can be predetermined by an initial adjustment made according to the scale. lt has been found, however, that upon making the same initial adjustment (using the same scale setting) in an innitely variable speed device, the output is not necessarily always the same.

In many applications, it is necessary to have both (a) a large number of different output speeds, and (b) a system wherein the output speeds obtained with a preselected setting of the device are always identical. In such applications, it is suiiicient to have a iinite number of difierent output speeds, but it is important that the speeds be known and reproducible.

Accordingly, an object of the present invention is to provide a transmission system adjustable to a finite number of output speeds which can be denitely ascertained by preselected settings of the system.

A further object of the present invention is togprovide such a transmission system which incorporates a plurality of gear units so coupled together that the number of different output speeds obtainable with the system is equal to the productof the total number of output speeds obtainable with each of the individual units.

Still a further object of the present invention is to provide a transmission system conforming with the preceding objects and incorporating a single input drive connection and a single output drive connection.

Yet other, and still further objects of the present invention are: (a) to provide a gear unit o-r box' having a plurality of primary gears, a plurality of secondary gears, and means for selectively coupling a given secondary gear with a given primary gear; (b) to provide a gear unit as prescribed in (a) above wherein the means for selectively coupling the primary and secondary gears comprises a rotatable cage carrying intermediate and/or idler gears in such a manner that preselected couplings between the primary gears and the secondary gears can be obtained by rotation of `the cage to preselected positions; (c) to provide a gear unit as prescribed in (a) above wherein the means for selectively coupling the primary gears and the secondary gears, is operable by means of pushbuttons; (d) to provide a gear unit conforming with the preceding objects set forth in this paragraph wherein the means for selectively coupling the primary gears with the secondary gears is so constructed that any given secondary gear can be selectively driven in either the same direction, or in the opposite direction to a primary gear coupled therewith; (e') to provide a gear unit according to the aforestated objects which can be easily contained within a comparatively small housing; and (f) to provide mathematical relationships and formulae which are characteristic of operation of gear units constructed in accordance with the invention.

An additional and still further object of the present invention is to provide a transmission system adapted to selectively produce a large number of finite reproducible output speeds, and including a plurality of gear units adapted to cooperate in plug-in fashion whereby the number of different output speeds can be conveniently and significantly increased by the addition of merely one gear unit.

Basically, and in its simplest aspects, the preferred embodiment of the invention provides a transmission system comprising an input shaft, a plurality of primary gears fixed on `the input shaft, a secondary shaft disposed in spaced parallel relation to the input shaft, a plurality of secondary gears fixed on the secondary shaft, and means for selectively coupling the primary gears with the secondary gears. The selective coupling means includes a plurality of intermediate gears in meshing relation with diiierent ones of the primary gears and means for selectively moving any one of the intermediate gears also into meshing engagement with one of the secondary gears whereby the secondary shaft is `driven at a preselected speed. Additionally, differential gear means is operatively connected with the input shaft and the secondary shaft, and the differential gear means includes a differential gear follower which is coupled with an `output shaft that is driven at the preselected speeds. Such a transmission system comprises a gear unit, according to the invention, and such a unit may be coupled with other units to provide for a greater number of preselectable output speeds in accordance with the invention. When the units are so coupled together, the input shafts of separate units are driven at different speeds by suitable means incorporated in the system, and an additional differential gear means is drivingly connected with the output shafts of different units. The additional differential gear means includes a diierential follower gear drivingly coupled with a single output shaft so that upon adjustment of the separate units, the single ultimate output shaft is driven at various preselectable and reproducible speeds.

The invention will be better understood, and objects` other than those specifically set forth above will become apparent, when consideration is given to the following detailed description of the exemplary embodiments of the invention. Such exemplary embodiments are presented in the annexed drawings, wherein:

FIGURE l is a cross-sectional view showing a preferred form of gear unit constructed in accordance with the present invention;

FIGURE 2 is a cross-sectional View of the output portion of the unit shown in FIGURE l, and an assembly provided in accordance with the invention for combining the outputs `of two gear units of the type shown in FIGURE 1;

FIGURE 3 is a perspective View of the preferred form of rotatable cage carrying intermediate and/ or idler gears provided by the invention for use in gear units of the type shown in FlGURE l;

FlGURE 4 is a schematic view 4of the gear unit shown in FEGURE l, FIGURE 4 being taken in a plane perpendicular to the plane of the drawing of FIGURE l, and presenting schematically the manner in which an intermediate gear cooperates with a primary gear and a secondary gear according to the invention;

FIGURES 5, 6, 7, 8, 9 land 10 are schematic views presenting the cooperative relationships between different sets 4of associated primary gears, secondary gears, and intermediate and/or idler gears in a gearV unit constructed in the manner shown in FIGURE 1;

FIGURE 1l is a schematic side view showing a modi- 3 fied form of the invention wherein selected coupling between the primary and secondary gears is achieved by means of push-buttons;

FIGURE 12 is a plan view of an overall transmission system provided by the present invention and including a plurality of gear units of the type shown in FIGURE l coupled together to provide for a multitude of selectable output speeds on a given single output shaft;

FIGURE 13 is a cross-sectional View showing a modified form of gear assembly for combining the outputs of two gear units so as to achieve a multitude f output speeds on a given single output shaft; `and FIGURE 14 is a cross-sectional View of a modified form of gear coupling assembly provided by the invention and used to drive input shafts of separate gear units in a predetermined ratio.

In FIGURE 1 the basic transmission system or gear unit provided by the invention is shown most completely, and by referring to that figure it will be noted that the numeral 2 has been used to designate the overall assembly. The assembly includes an input shaft 4 to which is coupled a plurality of primary gears designated as Pl-Pn. Disposed in spaced parallel relation to the input shaft 4, is a secondary shaft 6 which `carries a plurality of secondary gears designated as S1-Sn- Means in the form of a cage 8 carries and supports a plurality of intermediate gears, and `as explained in detail hereinbelow, such intermediate gears are in meshing relation with different ones of the primary gears. A handle device 10 is coupled with the cage S and adapted to rotate that cage, and thus such handle device serves as a means for selectively moving any one of the intermediate gears carried by the cage into meshing engagement with yone of the secondary gears. With such an arrangement, upon rotation of the handle device 10 the secondary shaft can be driven at preselected speeds according to the rotational position to which the cage has been moved.

The assembly 2 also includes a differential gear means 12 including a differential follower gear 14, and a suitable gearing arrangement 16 couples the secondary shaft with the differential gear means 12. The input shaft 4, as explained below, is directly coupled with the differential gear means 12, and thus the input shaft and secondary shaft are drivingly connected with the differential gear means. An output shaft 18 is drivingly connected Iwith the differential follower gear 14. Upon adjustment of handle device 1d and thereby the cage 3 to selectively drive the secondary shaft 6 at `a preselected speed, the differential gear means is operative, through the differential follower gear, to drive the output shaft 18 at a preselected speed in accordance with the selected movement of the cage S.

The gear unit 2 is preferably carried within a housing 24, having a divider wall 2% extending therethrough. The input shaft or drive shaft 4 passes into the housing 24 yand extends throughthe divider wall 2d. A gear 22 is fixed immovably to the divider wall 2d, and the shaft 4 passes freely through such gear 22. On the right hand side of the divider wall 2li as shown, the input or drive shaft 4 is fixedly coupled to a primary drive gear D1 of the differential gear assembly 12.

The secondary shaft 6 is, as stated above, disposed in spaced parallel relation to the input shaft 4, and extends between suitable vbearings 2e and 28 carried `on the left wall of the housing and right wall of the housing respectively as shown in FIGURE 1. The secondary shaft 6 passes through the divider wall 2d, and on the left hand side of the divider wall, the secondary gears Sl-Sn are fixedly secured to the secondary shaft A6. Gn the end `of the secondary shaft 6 adjacent the bearing 2S, there is fixed a gear 31 which cooperates with a gear 32 fixed for rotation with another primary drive D2 of the differential assembly 12.

The cage 8 which carries the intermediate gears is best shown in FIGURE 3. By reference to that figure,

it will be noted that disposed about the periphery of the cage are a plurality of intermediate gears ydesignated as Gn and a plurality of idler gears designated by In. In fact, according to the invention, one intermediate gear and one idler gear is provided on the cage for each primary gear.

The cage 8 is rotatably supported within the housing 24- by means of a bearing ring 30 (FIGURE 1) and cooperation of the handle assembly 1d with the left wall 31 of the housing. More particularly, the handle assembly 11i carries a bearing ring 34 which abuts against the youtside face of the wall 32 of the housing, and is provided with an internal threaded bore 36 with which the shaft-like projection 38 of the cage cooperates. Preferably a reduced threaded shaft 4d extends forward of the shaft 38, and a cap 42 is provided to iixedly secure the cage to the handle 10 so that the cage is rotatable with such handle.

when the cage is disposed in operative position as shown in FIGURE 1 between the input shaft 4 and the secondary shaft 6, then the primary gears may Kbe drivingly coupled with the secondary gears upon rotation of the cage or turning of the handle means 141. As stated, the cage carries an intermediate gear G and an idler gear I associated with each primary gear. The intermediate gear G is always in mesh with its associated primary gear as shown in FIGURES 540, and the idler gear I is always in mes-h with its associated intermediate gear. However, the secondary gears associated with each primary gear and each intermediate and idler gear do not mesh with anything unless the cage 8 is rotated so that either the intermediate gear G or idler gear I is meshing therewith. If the intermediate gear G associated with a given primary gear and given secondary gear is in mesh with yboth of such gears, then the secondary shaft 6 is driven in the same direction as the input shaft 4. However, if the cage is rotated so that the idler gear I associated with the given primary and secondary gears is in mesh with the secondary gear, then the secondary shaft is rotated in the opposite direction to the input shaft 4.

The primary gears Pl-Pn are of varying size or progressively increasing radius as shown in FIGURE 1, and the secondary `gears are of equal size and radius. However, it should be understood that the secondary gears can be of varying size or radius and the primary gears equal. As will be appreciated by those of `ordinary skill in the art, in a gear train, the important factor is the size of the first and last gears, which in this case are the primary and secondary gears. The intermediate gears are of cooperating sizes or radii so as to provide a drive between the primary and secondary gears. The size of the intermediate gears is irrelevant except in so far as suitable cooperation for drive between primary and secondary gears is concerned. The speed at which the secondary shaft 6 is driven is dependent upon the sizes of the particular primary gear and secondary gear that areV coupled together through an intermediate or idler gear. In the embodiment shown in FIGURE 1, the input shaft 4 carries a cluster of six gears, and the secondary shaft 6 also carries a cluster of six gears.

As stated hereinabove, the output shaft 18 is driven by the differential gear follower 14 and its speed is therefore equal to half the sum of the speeds of the input shaft 4 and the second differential drive gear D2. Thus if the speed of the input shaft is V1 rpm. and the speed of the second differential gear D2 is VD2 r.p.m., then the speed of the output shaft 18, V18, is equal to In this expression, the speeds are `considered as positive if the rotation is clockwise, and negative if the rotation is counterclockwise. When the cage S is rotated to a position where one of the intermediate gears G is meshed with the corresponding secondary gear S, then the secondary shaft 6 will rotate in the same direction as the input shaft 4, and the second differential drive gear D2 will rotate in the opposite direction. According to Equation 1, theretore, the output speed, namely, the speed of output shaft 18, will be one-half of the Idifference between the two speeds (V1-V132).

If, however, the cage is rotated until one of the idler gears I engages'with the corresponding secondary gear S, then the second differential drive gear D2 will rotate in the same direction as the input shaft 4 (i.e., VD2 will be positive if V1 is positive), and the output speed of the output shaft 13 will be one-half of the sum of the two yspeeds (Vl-f-VDZ).

In addition to carrying intermediate gears and idler gears corresponding to each of the primary gears, the cage 8 also carries a zero gear GX. Moreover, the secondary shaft carries a corresponding secondary gear SX. If the cage is yrotated until the intermediate gear GX engages the secondary gear SX, then the secondary shaft will be locked because Gx meshes with Xed gear 22 carried on intermediate or divider wall 20. Accordingly, in this instance, VD2=0, and the output speed will be Vlzl/z V1.

If the ratio of the primary and secondary diierential drive speeds is denoted by R, then the speed of the second differential gear D2 can be given as VD2=RV1 (2) In this expression, R Will be positive if an idler gear is engaged with the secondary gear, and will -be negative if an intermediate @gear is engaged with a secondary gear. Taking from Equation 2 above the value of VDZ, and substituting the same in Equation 1 gives Accordingly, if the overall speed ratio of the gear unit is designated by SR, then SR=1/z (l-i-R), and R=2SR-1. The following table sets forth various values of SR with given values of R. `It will be seen from the table that with .the assembly described, the overall speed ratio of the unit can be varied from to 1 in increments of .l merely by selecting gears in such a manner that R has the values listed.

While we have not described in minute detail the cooperation between each set of primary gear, secondary gear, intermediate gear, and idler gear, a review of FIG- URES 5-10 will show the relative positioning of the intermediate andY idler gears around the cage 8 so that rotation of such cage results in a driving of a given secondary gear by means of a given primary gear. Moreover, the comparative sizes of the primary gears and intermediate gears will become apparent, and it will be noted that the primary gears have increasing radii while the intermediate gears have decreasing radii. Additionally, from a review of FIGURE 4, it will be seen that in the overall assembly, the peripheries of the intermediate and idler gears lie along the same circular locus 100 so that rotation of the cage S results in placing either an intermediate gear or an idler gear alternately in cooperative engagement between a primary gear and a secondary gear.

Notwithstanding the fact that the embodiment of the invention described hereinabove provides for utilizing a cage carrying and supporting the intermediate and idler gears, the invention `also contemplates the utilization of various other types of selective control means, including push-button means. Particular attention is directed to FIGURE 1.1 ywherein it will be noted that the intermediate and idler gears G and I respectively are supported on a rocker arm 102 which is journaled about the input shaft 4. Push-buttons 104 and 106 are incorporated for selectively moving the rocker arm 102 so that either the intermediate gear G meshes with the secondary gear S, or alternatively, the idler gear I meshes with the secondary gear S.

yPreferably the rocker arm 102 which carries the intermediate gear G and idler gear I is provided at one end thereof with a series of recesses such as those designated by numerals 10S, 110 and 112 in FIGURE 11. Additionally, the housing or other suitable support carries a spring-pressed ball detent 114- which cooperates with the recesses. Thus, if the push-button 106 is depressed, the rocker arm 102 rotates clockwise and the detent 114 cooperates with the recess 112 to maintain the rocker arm in such a position that the idler gear I meshes with the secondary gear S. To restore the rocker arm to its neutral position, one need merely press the push-button 104. Moreover, if it is desired to place the intermediate gear G and secondary gear S in meshing relationship, and the rocker arm is in the neutral position shown, then upon depression of the push-button :104, the rocker arm is moved suitably and the detent i141 cooperates with the recess 108. After the rocker arm has been so rotated counter-clockwise, it can be restored to neutral position by pushing the push-button 106.

It should be apparent that although we have described only one rocker arm and intermediate and idler gear arrangement, such an arrangement can be provided for each set of primary and associated secondary gears, and accordingly the push-button arrangement would provide essentially the same system as that shown in FIGURE 1, except the cage 8 would have been replaced by the rocker arms, and the handle means 10 would be replaced by the push-buttons. Moreover, preferably means of any wellknown type is provided for preventing the depression of more than one button at any given time so as to eliminate jamming of the box.

From the foregoing discussion, it should be apparent that by utilizing a differential gear means, the invention provides for obtaining a iinite number of different output speeds on a single shaft, which speeds are the result of rotation of two different shafts, namely, the input shaft and the secondary shaft. This same principle can be applied, according to the invention, to an overall transmission system incorporating two separate gear units. In other words, the output shafts 18 of two individual gear units can be coupled through a suitable dierential gear means, and the differential follower gear of such gear means can be connected to a single output shaft. When such overall system is utilized, the number of finite output speeds is equal to the product of the number of output speeds produceable by each of the units.

In FIGURE l2 we have shown one such overall system. Two units 2 are incorporated, and each of the units has a handle means y10 for adjustment thereof. The input shaft 4 of the right hand unit shown in FIGURE 12 is coupled with the input shaft 4 of the left hand unit shown in FIGURE 12 by means of a drive which causes the input shaft of the left unit to be rotated at a fraction of the speed at which the input shaft -of the right unit is driven. More particularly, a motor 200 having a shaft 202 is coupled directly by means of a collar 204 with the input shaft 4 of the right unit. The shaft 202 carries a bevel gear 206 cooperating with a bevel gear 20S carried by the cross-shaft 210. The cross-shaft 210 is journaled in a suitable block 212 and carries at the left end thereof a worm 214. The worm 214 cooperates with a meshing gear 216 fixed to the input shaft 4 of the left unit and 7 drives the same. if the units are constructed in accordance with the ratio set forth in Table I hereinabove, and if the left units input shaft 4 is driven at /l@ the speed at which the right units input shaft is driven, then the assembly of FIGURE 12 can be adjusted to produce l0() different output speeds variable at .0l intervals.

The preferred manner in which the outputs of both units are coupled together may be best understood by reference to FIGURE Z. In that figure, the output shaft iS of one unit is shown as extending within an output casing 3th). The output shaft 18 carries a bevel gear 3&2 which cooperates with and drives a meshing bevel gear 3M- carried on a shaft 396 suitably journaled within the housing 35i@ and drivingly connected with the primary driving gear D1 of an output differential gear mechanism 3ft?. The output shaft of the left unit 2 shown in FlGURE 12 can be directly coupled with the shaft Il?. shown in FGURE 2.

in the FGURE 12 embodiment, the output shaft 4 of the left unit is shown as being coupled with the shaft 312 of FIGURE 2 by means of a pair of cooperating bevel gears 324i and 322. However, any suitable coupling may be used.

Upon examination of FIGURE 2, it will be apparent that the shaft 312 is coupled through the gearing arrangement including gears 330, 332, 334 and 336 with the primary drive gear Dl/Z of the differential gear mechanism 310. The shaft 33S is suitably journaled within the output housing or section 300 so as to carry the gears in the cooperating arrangement shown. The differential gears `Dfi/ll and D1/2 of the differential means Siti drive the differential follower gear D1/3 which is drivingly connected to output shaft 350 which passes freely through gears 336 and D1/2.

It should be pointed out that the output from the second or additional differential gear means 310 is present on shaft 356. Moreover, it will be understood that the input shaft from an additional unit, namely, shaft 3:12, can be provided with female couplings and the output shaft 13 of a unit can be provided with a male coupling so that the units can be coupled together in plug-in fashion.

One additional factor which should be considered is that when the assembly of FGURE l is provided with the second differential gear mechanism as shown in FIGURE 2, and yet it is only desired to use one unit, then the input coupling 312 `must be plugged and stopped from rotating in order to prevent the output shaft from not rotating when `a load is applied thereto.

While we have shown a suitable input connection mechanism -between two gear units in FIGURE 12, and While we have shown a suitable second or output differential gear mechanism for use with two units in FIGURE 2, the invention provides for certain modified forms of each of the units.

in FIGURE 13, a modified `form of differential output assembly is shown. The output shafts i8 of each unit carry bevel gears dit@ and ddii. These bevel gears cooperate with -bevel gears @ffii and 402i respectively which are carried by lsuitable shafts 404 and 404 respectively. Shaft itl-t is drivingly connected with a primary driving gear 4% of an output differential assembly 463, and shaft ddd is drivingly connected with a primary differential driving gear el@ of the output differential assembly 40S. Bevel pinion gear 4t2 is part of the differential gear assembly of 463, and such gear is suitably coupled to a planetary cage 42@ which is fixed to a bevel gear 422. An output shaft .124 carries at one end thereof a bevel gear 426 which meshes with the bevel gear 422 carried by the cage. This differential gear means is essentially the same in operation as the differential gear means 310 described in FIG- URE 2, however it is a somewhat simpler differential gear arrangement for operating an output shaft.

Now, in addition to utilizing an input drive between two units of the type shown in FIGURE 12, the invention provides for utilizing a somewhat simplified plug-in form of input feed arrangement, as shown in FIGURE 114. By reference to that figure, it will be noted that the motor drive is fed to an input shaft 90 suitably journaled in an input housing S412. The shaft 5MB' carries a bevel gear 56M which cooperates with a bevel gear 5% fixed to the input shaft 4 of one of the units. Additionally, the input shaft Sti@ `carries a gear 98 which meshes with `a gear Siti carried on an idler shaft 512. The idler shaft 512` is also suitably journaled within the vhousing and carries `an additional gear 514 at one end thereof. Gear 514 cooperates with a gear 5ft; suitably attached to a `shaft 518 which can be directly coupled with the input shaft of the next unit. The input shaft preferably is provided with a female connection, and the output shaft 51S is preferably provided with a male connection so that the units can be assembled in plug-in fashion. As will be appreciated by those of ordinary skill in the art, gear train tlS-Sltl-Sit-lf provides a reduced speed drive for the next unit.

From the foregoing description of the invention, it should be apparent that the objects set forth at the outset of this specification have been successfully achieved.

What is claimed is:

1. A transmission system comprising an input shaft, a plurality :of primary gears fixed on said input shaft, a secondary shaft, a plurality of secondary gears fixed on said secondary shaft, at least one of said pluralities of gears including gears of different radii, means supporting `a plurality of intermediate gears in meshing relation with different ones of said primary gears, means for selectively moving any one of said intermediate gears also into meshing engagement with one of said secondary gears whereby said secondary shaft is `driven at a preselected speed, differential gear means including a differential follower gear, means drivingly connecting said secondary shaft to said differential gear means, and an output shaft drivingly connected to said differential follower gear lwhereby said output Ashaft is driven at a preselected speed in `accordance with the selected movement of one of said intermediate gears into meshing engagement with one of said secondary gears.

2. A transmission system as defined in clai-m 1 wherein said means for supporting a plurality of intermediate gears comprises a plurality of rocker arms, and wherein said means for selectively moving any one 'of said intermediate gears comprises push-button means.

3. A transmission system as defined in claim 2 wherein each of said rocker arms carries a separate intermediate gear and an idler `gear meshing therewith, and wherein said push-button means `comprises a pair of push-buttons operatively linked to each of said rocker arms for selectively moving the intermediate gear or the idler gear carried on a given rocker arm into meshing engagement with an associated secondary gear whereby said secondary shaft is rotatable at a speed, as Well as in a direction, selectable by said push-button means.

4. A transmission system comprising an input shaft, a plurality of primary gears of different radii fixed on said input shaft, a secondary shaft disposed in spaced parallel relation to said input shaft; a plurality of secondary gears fixed on said secondary shaft, a rotatable gear cage surrounding said input shaft :and primary gears, said rotatable cage carrying a plurality of intermediate gears angularly spaced with respect to one another, said intermediate gears always meshing with an associated primary gear, said cage being rotatable to selectable positions where given ones of said intermediate gears mesh with given ones of said secondary gears, whereby said secondary shaft is driven at selectable speeds, differential gear means drivingly coupled With said input shaft and said secondary shaft, said differential gear means including a differential `follower gear drivingly coupled with an output shaft whereby said output shaft is driven at a preselected speed corresponding to the selected position to which said cage has been rotated.

5. A transmission system as defined in claim 4 wherein said cage carries for each primary gear an intermediate gear and an idler gear meshing with, and having its periphery aligned with intermediate gear whereby said cage can be rotated to a plurality of selectable positions where a given one of the intermediate gears or idler gears meshes with a given one of said secondary gears and said secondary shaft is rotated in a direction and at a speed corresponding to the selectable position to which said cage has `been rotated.

6. A transmission system comprising at least a pair of gear units, each of said units including an input shaft, a plurality of primary gears fiXed on said input shaft, a secondary shaft disposed in spaced parallel relation to said input shaft, a plurality of secondary gears fixed on said secondary shaft, means supporting a plurality of in termediate gears in meshing relation with different ones of said primary gears, means for selectively moving any one of said intermediate gears also into meshing engagement `with one of said secondary gears whereby said secondary shaft is driven at `a preselected speed, rst differential gear means including a first differential follower gear, means drivingly connecting said secondary shaft to said rst differential gear means, and a first output shaft drivingly connected to said first differential follower gear whereby said output shaft is driven at a preselected speed in accordance with the selected move ment of one of said intermediate Igears into meshing engagement with one of said secondary gears; means for driving the input shaft of one .of said units at a fraction of the speed at which the input shaft of the other of said units is driven; second differential gear means including a second diiferential gear follower, means drivingly connecting the output shafts of said units to said second differential gear means, and a second .output shaft drivingly connected :to said second dierential follower gear whereby the speed of `said second output shaft is preselectable in accordance with the selected movement of the intermediate gears in each of said units.

7. A transmission system as defined in claim 6 wherein said means for supporting a plurality of intermediate gears comprises a plurality of rocker arms, and wherein said means for selectively moving any one of said intermediate gears comprises push-button means.

8. A transmission system as defined in claim 7 wherein each of said rocker arms carries a separate intermediate gear and an idler gear meshing therewith, and wherein said push-button means comprises a pair of push-buttons operatively linked to each of said rocker arms for selectively moving the intermediate gear or the idler gear carried on a given rocker arm into meshing engagement with an associated secondary gear whereby said second-` ary shaft is rotatable at a speed as well as in a direction selectable by said push-button means.

9. A transmission system comprising a pair of gear units, each of said units including an input shaft, a plurality of primary gears of different radii fixed on said input shaft, a secondary shaft disposed in spaced parallel relation to said input shaft, a plurality of secondary gears fixed on said secondary shaft, a rotatable gear cage surrounding said input shaft and primary gears, said rotatable cage carrying a plurality of intermediate gears angularly spaced with respect to one another and of varying radii, said intermediate gears always meshing with an associated primary gear, said cage being rotatable to selectable positions where given ones of said intermediate gears mesh with given ones of said secondary gears whereby said secondary shaft is driven at selectable speeds, first differential gear means drivingly coupled with said input shaft and said secondary shaft, said diierential gear means including a rst differential follower gear drivingly coupled with a first output shaft whereby said first output shaft is driven at a preselected speed corresponding to the preselectable position to which said cage has been rotated; means for driving the input shaft of one of said units at a fraction `of the speed at which the input shaft of the other of said units is driven; second differential gear means including a second differential gear follower; means drivingly connecting the iirst output shafts of said units to said second differential gear means, and a second output shaft drivingly connected to said second differential follower gear whereby the speed of said second output shaft is preselectable in accordance with the selected movement of the intermediate gears in each of said units.

10. A ltransmission system as `defined in claim 9 wherein said cage carries `for each primary gear an intermediate gear and an idler gear meshing with, and having its periphery aligned with said intermediate gear whereby said cage can be rotated to a plurality of selectable positions where a given one of the intermediate gears or a given one of the idler gears meshes with a given one of said secondary gears and said secondary shaft is rotated in a direction and at a speed corresponding to the selectable position to which said cage has been rotated.

11. A transmission system as ydened in claim 10` wherein said cage comprises a cylindrical ring and wherein said intermediate gears and said idler gears are journaled in slots in said ring whereby they extend between the inside and outside arcuate surfaces of said ring.

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